Method and apparatus for lapping color film embossing rollers



" Patented Sept. 15, 1931 uni-so sraras PATENT OFFICE OTTO WITTEL, OFROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER,NEW YORK, A CORPORATION OF NEW YORK METHOD AND AEPARATUS FOR LAPPINGCOLOR FILM EMBOSSING ROLLERS Application filed. October 29, 1928. SerialNo. 315,771.

This invention relates to lapping minute grooves or serrations onrollers for embossmg film for color motion pictures. One object of myinvention is to provide a method I a of obtaining a series ofexceedingly small grooves in a roller which are of similar shape,

dimensions, and which have a highly polished surface. Another object isto provide a lapping tool with which such grooves may be 110 made.Another object is toprovide a wire lapping tool on which wires areprovided for the lapping operation and which are held under sprintension. Another object is to provide a wire-holding means which isconstructed to hold each wire accurately in a predetermined position,and other objects will appear from the following specification, thenovel features being particularly pointed out in the claims at the endthereof.

Coming now to the drawings, wherein like .reference characters denotelike parts through,--

Fig. 1 is a view partly in elevation and partly in section of a filmembossing roller constructed by the method and with they apparatus madein accordance with my invention;

Fig. 2 is a side elevation of a lapping tool constructed in accordancewith a preferred embodiment of my invention;

Fig. 3 is a 'top plan view of the lapping tool shown in Fig. 2;

Fig. 4 is an enlarged side elevation of one of the wire-holding posts ofthe lapping tool;

Fig. 5 is a highly magnified fragmentary sectional detail illustratingthe action of the lapping wires upon the embossing roller;

Fig. 6 is an enlarged sectional view through a portion of a wire-holdingpost;

Fig. 7 is a fragmentary detail showing the surface of a cylinder havingthe (preliminary etched or cut grooves therein; an

Fig. 8 is an enlarged fragmentary detail indicating a possible relationbet-ween a film being embossed and'an embossing roller constructed inaccordance with my invention.

In certain systems of color photography the film is embossed with aplurality of extremely fine lenticular areas and these areas may be madeby embossing the film with a roller which has grooved or serratedperiphery. The lenticular areas or elements formed in the film areextremely minute as, for instance, in a preferred type of film thedistance across these elements may be from .0015 to .002 of an inch. Itis to be understood, of course, that these dimensions may varyconsiderably, but the lenticular elements are always extremely small.

In order to provide an embossing roller for the'film, with very sharppoints which will press into the film when rolled upon it underpressure, I have provided a method and apparatus which will now be fullydescribed.

It is to be understood that my method and apparatus may be used inmaking a completed cylinder which may be used directly to roll t elenticular elements into the film, or it may .be used for making a toolwhich is used to transfer an impression to a second tool, which later isused to make a final film embossing roller. It is sometimes preferableto make the roller through a series of steps, because when this is done,in making the two preliminary tools, it is easier to make the first toolcomparatively small in width, the second somewhat larger, and the thirdfilm embossing roller can readily be made of considerably greaterdimensions than either of the tools used in making it. This system formsno part of my invention.

As shown in Figure 1, a grooved embossing cylinder may consist of anannular member 1, having a plurality of very fine grooves 2, formed inits surface. Because of the extremely small size of these grooves, thedrawing is nowhere near to scale. A cylinder 1 is first made with asmooth, accurately ground and polished, outside periphery which may bethen covered with a resist, such as wax, and a fine line scratchedthrough the wax, after which the cylinder is etched, leaving more orless irre lar grooves, as indicated at 3 in Figure Instead of etching,these grooves may be out upon a lathe, but, in any event, the groovesare not of either the proper size or width. The spacing between thecenters of grooves indicated at S in Figare 7 should be the width whichis desired between the final grooves in the roller. This may be, say,.0018 of an inch.

With the roller grooved by etching or cutting, as above described, thegrooves are made perfect in shape and the points between the grooves aresharpened by means of a lapping operation and with a lapping tool whichwill now be described.

As indicated at Figure 2, the lapping tool ma comprise an L-shapedmember 4, to WlllCll there is pivoted at 5 an arm 6, which is pressedabout the pivotal point in the direction indicated by the arrow by meansof a spring 7. Each of these members,- that is, members 4 and 6, carrywire-holding posts 8. These posts may be held by screws 9 on theirrespective mounts and, as indicated in Figure 4, are preferably providedwith a #0 thread 10 about which the wires 11 are wound.

Around portions of the threads 10, after they have been wrapped withwires 11, there is placed a section of shellac or varnish 12 which, asindicated in Figure 6, cements and 86 holds the various wires in thebottom of the 4 threads 10.

The L-shaped member 4 and the hinged member 6, with theposts 8,constitute a spring support for the wires 11. By placing an end 17 ofthe spring in different apertures 18, the

desired tension can be maintained.

Since it is very diflicult to cut a thread having as small a pitch as.0018, as would be required for lapping the grooved cylinder of.

I Figure 7, I preferably provide the thread 10 of a pitch considerablygreater than .0018, but of a multiple thereof. For instance, there maybe one thread 10 for every four grooves on the roller, so that with thelap- Q ping wires spaced as shown in Figure 6, each wire would tend topolish every fourth groove in the roller and by moving the lapping toolgradually up and down the surface of the cylinder, all of the grooveswill finally be shaped and polished.

- The size of the wires relative to the grooves is also important.Referring to Figure 5. if the'final spacing of the grooves indicated at(Z is desired to be .0018, the radii of curvalo ture R may be the samedimension as the spacing and if this is so, the radius of the lappingwires '1' should be slightly less than the radius of the grooves, inthis case, 1" being .0015. This difference in the radii permits acertain 56 amount of lapping compound L to lie between the lapping wiresand the grooves.

The first of the lapping operation is performed with very fine emerywater and the final polishing is performed with rouge. The

- 60 lapping operation with a steel cylinder of comparatively smalldimensions, such as, for instance, approximately the width of a 16 mm.motion picture film, may take from eight to sixteen hours.

55 During this time the wires 11, which, of

course, are very small, may wear out and break. A careful operator runsthe lapping tool slowly up and down so that different parts of the wiresare brought in contact with the rotating cylinder. Should certain wiresbreak, these wires may be pulled off, the shellac 12 holding theremaining wires in place.

Aftera number of the wires become broken,

a new lapping tool may be readily prepared for olishing minute groovesin cylinders provides grooves having accurate radii of curvature and isespecially useful in that regular sharp points 13, as shown in Figure 5,separate the smooth curved walls 14 from each other.

Attention is directed to the fact that in embossing film itis believedthat the film.

does not entirely touch the surface 14 of the grooves. Obviously, wherethe dimensions are so small, it is very difiicult to say whether or notthis is true. acts, as indicated in Figure 8, while being rolled,--thatis, the curvature of the film is somewhat less than the curvature of thegroove. Measurements under a microscope indicate that where the totaldepth ofthe groove, as indicated at 15, is, for instance, .0005 of aninch, thetotal height indicated at 16 of the film embossings may be.0004 of an inch. i I am not prepared to say that the film does notactually contact with the surface 14 and then after the rollingoperation is over spring back the .0001 of an inch of a difference.

However, it is well known that in order to retain a most perfect polish,a cellulosic film can only contact with a highly polished surface, forifit is brought in contact with a slightly matte or roughened surface,this surface will be imparted to the film. With the method and apparatusdescribed in this application, the film lenticular elements have ahighly polished, perfectly satisfactory surface for producing the minuteimages on the emulsion side of the film.

I believe that it is only necessary inorder to produce accurate, minute,lenticular elements on a film band to provide a row of sharp projections13, which are regularly spaced. If these points are sufficiently strong,it is not material how: deep the groove 14 lying between the points maybe. However, the film is rolled on these projections under considerablepressure and because of The method which I have just described But Ibelieve the film.

the extremely minute size of the projections, these are liable to breakor to become distorted.

With the lapping operation, as above described, the points 13 are sharpand yet the 'ridges are comparatively thick through. the

1 However, I do not wish to be limited to any particular metal asobviously other materials would be entirely satisfactory.

The annular member 1 is preferably made of cold-rolled steel, as thismetal can be readily worked in the manner described above, and as it issufliciently hard to stand up under the necessary pressure used inembossing the film. However, it is obvious that other grades of steel orother metal can be used if desired. The periphery of the member 1,thatis, the grooved face 2, can be protected from rusting, if desired, witha very thin layer of plating chromium, but this may be omitted if careis taken in using the roller to prevent rust.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A method of lapping lenticular film embossing rollers which comprisesproviding a cylinder with a plurality of fine guide lines, turning saidcylinder, and lapping with a plurality of wires, a fine lapping compoundbeing used on the cylinder.

2. A method of lapping lenticular film embossing rollers which comprisesproviding a cylinder with a plurality of fine guide lines. turning saidcylinder and moving wires under tension over the rotating cylinder, thewires being positioned by the guide lines, and applying a very finelapping compound between the wires and cylinder.

3. A method of lapping lenticularfilm embossing rollers which comprisesroviding a cylinder with a plurality of ne guide grooves breaking thesurface of the cylinder, lapping said grooves with a'lapping compoundand with wires of slightly less diameter than the grooves to be made inthe cylinder, and continuing the lapping operation until the groovesareenlarged to the desired size, said operation also polishing the groovesin the periphery of the cylinder.

4. A method of lapping lenticular film embossing rollers which comprisesproviding a cylinder with a plurality of fine guiding grooves, andenlarging said grooves by lapping with a plurality of fine wires, saidwires e1 other than the guiding grooves.

5. A method of lapping lenticular film embossing rollers which comprisesproviding a cylinder with a plurality of fine guiding grooves, andenlarging said grooves by lapping with a plurality of fine wires, saidwires being spaced at greater distances from each other than the guidinggrooves, said spacing being multiples of the spacing of the guidinggrooves.

Signed at Rochester, New York, this 22nd day of October 1928.

' OTTO WITTEL.

ng spaced at greater distances from each

